1. Field of the Invention
This invention relates to an improved method for making members of position measuring apparatus having thereon patterns of uniformly pitched bars, and to members made by such method.
2. Description of the Prior Art
Precision position measuring apparatus with members having thereon patterns of uniformly pitched bars alternating with spaces are well known in the measurement art. One of the most accurate of such transducers is that manufactured under the trademark INDUCTOSYN and described in U.S. Pat. No. 2,799,835. The INDUCTOSYN transducer is a high accuracy multipole position measuring transformer manufactured in both linear and rotary forms. In either form the transducer employs two relatively movable members, each having a pattern of uniformly linearly or angularly spaced conductor bars positioned thereon by, for example, a photoetching process. The precision and the accuracy of the transducer depend directly upon the uniformity of pitch and positional accuracy of the pattern of conductor bars on its members.
Position measuring instruments which make use of optical rather than electronic techniques also have members with patterns of uniformly spaced bars thereon. Well known transducers of this type include optical shaft digitizers, and devices which employ two superimposed but slightly skewed linear optical gratings to generate fringes which may be counted to measure the relative displacement of the two gratings. Such optical position measuring transducers also depend for their accuracy directly upon the unformity of pitch of the bar pattern on their members.